BURLINGTON — Sen. Bernard Sanders, I-Vt., said the warmest year on record in the United States and in Vermont has persuaded him it’s time to get serious about climate change.

Sanders said he will introduce legislation that includes a tax on greenhouse gas emissions from the biggest polluters, more money for energy efficiency, and clean energy research and development.

He said the measure also would end tax breaks and subsidies for fossil fuels.

Sanders’ announcement followed word from the National Climatic Data Center in Asheville, N.C., that the mean U.S. temperature last year was 55.32 degrees, a full degree warmer than the old record set in 1998.

The mean 2012 temperature in Burlington was 50 degrees, also beating a record set in 1998.